Synthetic adsorbent for separating hydrocarbons



Patented May 25, 1948 2,442,191 srm'rnerrc ADSOBBENT Foasnraaa'rme mzrmoclmno 1...... F. Black,

Roselle, N. 1., assixnor to Standan! Oil Development Company, acorporation Delaware No Dra Serial N0. 537,529.

wing. Original appllcation May 26, 1944, Divided and this applica tion June 23,1945, Serial No. 001,329

(or. 252-210) j 15 Claims.

The present application is a division of my copending application, Serial No. 537,529, filed May 26. 944.

It is desirable in many operations to remove normal parafilns from petroleum oil refinery gases since they would otherwise pass through a treating system as inert and reduce the capacity of a system to function in the desired manner to the extent of their presence in the original feed stock. For example, in the alkylation of isoparafiins with olefins, the isoparaflln, such as isobutane, is invariably associated with n-parafiins and of course the n-parafllns pass through the alkylation unit unchanged. To prevent the accumulation of this inert n-parailin in the alkylation system, it is necessary to fractionate the unreacted isoparaiiins which are recirculatedto the reaction zone to remove the n-parafllns from the system and/or to maintain the quantity thereof below a certain maximum. I have discovered that n-parafilns may be separatedirom a mixture of normal and isoparafllns, naphthenes and aromatics by adsorption on a material hereinafter fully identified.

Another important aspect of my invention involves the removal of n-paraffins from a naphtha. Suppose that a naphtha contained paraffins as well as, say, naphthenes, isoparafiins and some aromatics, I may improve the octane number of that naphtha by causing the removal of a substantial quantity of n-paraflins by an adsorption method which will be explained more fully hereinafter.

The main object of my invention, therefore, is

to provide an absorbent adapted to effect the separation of straight-chain hydrocarbons, such as n-parafilns, from other hydrocarbons in a more economical and expeditious manner than has heretofore been accomplished.

Other and further objects of the present invention will appear from the following description and claims.

I have found that a mixture of hydrous oxides of aluminum and. silicon with a hydroxide or oxide of a group Ii metal of the periodic system. such as calcium oxide, is adapted to react together to form a substance exhibiting specific adsorption capacity for normal para'fl'lns, if the said oxide and hydroxide mixture is heated, preferably with a solution '0: a salt of the group II element, to a temperature in the range of from 0 C. to 500 0., preferably from about 220 to about 400 C. The material produced after dehydration by heating in vacuo, is adapted for removingn-parafllns and/or n-olefins from mixtures of straightchain hydrocarbons, isoparamns', naphthenes and aromatics.

I shall set forth in Example: 1

Calcium hydroxide, aluminagel (precipitated from aluminum nitrate with ammonia and and'siliea gel (Davisons." mixed in the ioliowing Y washed free-or salts) washed silica gel) were 7 mol proportions, based on the oxides, to wit; of 4Ca0, A1203, 4810a and rotated three hours in a ball mill containing small stones. The-product was dried at 250 F. and forced througha screen to form granules of a sizerot 1*; to %inch in. diameter. 200 cc. (approximately 20 grams) of calcium acetate -a- .1,.-z 0 b and this material and 2 liters of a 1% solution were sealed in h heated at 220 C. for-.84 hours in arocker to provide agitation. The pressure within the bomb was determined by the vapor pressure of the calcium acetate solution and the pressure of the 2- liters of air which were closedin when the bomb was sealed at room temperature. The absolute pressure resulting was about 360 lbs. per square inch.- After the heating period the. bombwas allowed to .cool, opened, and the contents-L filtered These'were washedon the s filter with distilled water @anddried at 200? F. After being dehydratedundervacuum at.500 0.. the product was found to be-adapted=toadsorb at mm. pressure, the-following amounts of to recover the solids.

gas expressed as cc. perwgramtof said :product corrected to 0 176 F. 23o" r. sit r; 424'r;*- 49191.

n-butane 4.5 .4.1. 4.1 2.2 1.3 iso-butane 0. 22 0. 26 0 0 A check run was made: the same ,condirj.

d-ani 8 1 pressure of. am, and: 0.05 cc.-

tions of synthesis. Thejproduct tion capacity at 36371". and; 1001 2.80 cc. normal butane" per g H isobutane per gram; This is 1a" good 3 agreement with the value of'2.90,iceg'mbiitan g er gram which can be H former product at"363" v average capacity of the product prepared under these specific conditions is,ntherefore, 2.85 cc. n-butane (S. T. P.) per gram,

obtainetilforflthe adsorpti n of the n'-butane.

C. are advantageous for the more rapid producthe latest. specific as... ples several embodiments. of my invention;

C. and latmosphere pressure:

tion of adsorption activity in the product. The effect of synthesis temperature is illustrated in the following examples:

Example 2 The synthesis wascarried out under the conditions 01' Example 1, except that a reaction time of only 48 hours was allowed. This decreased the adsorption capacity for n-butane at 363 F. and 100 mm. pressure from 2.85 per gram for the substance from Example 1 to 0.44 cc. per gram for this material.

. Example 3 Example 4 The synthesis was carried out under the conditions of Example 1 but a slightly longer synthesis time of 96 hours instead of 84 hours was employed and the synthesis temperature was dropped to 160 time the product had an adsorption capacity at 363 F. and 100 pared to that of 2.85 cc. uct 01' Example 1.

- Example 5 The synthesis was carried out under the conditions 01' Example 1, except that a synthesis temperature of only 100 C. was employed. There was hardly any detectable adsorption evidenced by the product.

The possibility to use salts oi. group II elements other than the acetate is shown by the following example:

per gram for the prod- Ezample 6 The synthesis was carried out under the conditions oi Example 1, except that a calcium chloride solution was used in place of the 1% calcium acetate solution. of the product was substantially the same, being 2.73 cc. per gram at 363 F. and 100 mm. compared to 2.85 cc. per gram for Example 1. In addition, the solution eiiected corrosion of the bomb giving an orange product containing 3.73% Fezm. This corrosive action is not evidenced when calcium acetate solution is employed.

The beneficial efiect of increasing the concentration of the group II salt in solution in the liquid ph e charged to the bomb is illustrated in the following example:

Example 7 Example 8 The synthesis was carried out under the conditions of Example 7, except that a heating time of 216 hours was employed. The product showed mm. of only 0.45 cc. per gram com- The adsorption capacity an adsorption capacity for n-butane at 363 F. and 100 mm. pressure of 4.85 cc. per gram compared to 3.15 cc. in Example 7. I

The ability to use other forms of alumina and silica is shown by the following example:

The synthesis was carriedout under the conditions of Example '1 and with a starting charge of the same chemical composition, except that it was prepared by grinding calcium hydroxide alumina tri-hydrate, (a commercial crystalline product having the formula AlzOa.3HO of a very low soda content) and impalpable, air blown C. In spite of the longer reaction .1

silica gel together in a mortar. The product adsorbed 0.63 cc. per'gram at 363 F. and mm. pressure of n-bu'tane. The synthesis is possible, therefore, with these materials but is more readily eifectedwhen using the gel mixture procedure described above.

The adsorption on all the products from the various examples cited should be specific in character. This is indicated by the similarity of the X-ray patterns of the various products showing the same compound to have formed and by check runs on the isobutane adsorption of some of them.

These were run at 363 F. and 100 mm. pressure of isobutane and showed:

The solid substance prepared by the methods I have indicated is a white powder which is packed into glomerates of moderate strength by drying from the form of a moist cake. The liquid phase filtered from the bomb at the end of a synthesis run contains no metallic elements other than the group H metal due to the soluble salt employed and solubility of the group II hydroxide in the solid charge. The overall chemical composition of the solid, therefore, is the same as that of the starting charge. r

The crystal structure of the product as indicated by its X-ray difiraction pattern does not agree with that of any or more than 1000 natural minerals and synthetic chemicals available for comparison I The experimental results from the examples cited indicate that the most favorable-synthesis conditigns are to employ high concentrations of a group'II salt in the liquid phase charged to the bomb. The temperatures used for synthesis should be substantially higher than 220 C. and the heating time should be of the order of one week. High synthesis temperature would enable the employment of shorter heating times.

While-subatmospheric pressures give good reand which is prepared by reacting a hydrous oxide of aluminum, 2. hydrous oxide of silicon and'oal- ..um hydroxide for a period of from 48 to 216 hours at a temperature between 100 and 500 C., cooling to room temperature and dehydrating.

2. A new composition of matter adapted to adsorb straight chain hydrocarbons consisting essentially or a solid adsorptive material having the empirical formula based on the oxides and which is prepared by reacting a hydrous oxide of aluminum, a hydrous oxide of silicon and calcium hydroxide for a period of from 48 to 216 hours at a temperature between 220 and 400 0., cooling to room temperature and dehydrating.

3. A new composition of matter adapted to adsorb straight chain hydrocarbons consisting essentially of a solid adsorptive material having the empirical formula based on the oxides and which is prepared by reacting a hydrous oxide of aluminum, a hydrous oxide of silicon, calcium hydroxide and an aqueous solution in about 1 to concentration of a calcium salt for a period of from 48 to 216 hours at a temperature between 100 and 500 C., cooling to room temperature and dehydrating.

4. A new composition of matter adapted to adsorb straight chain hydrocarbons consisting essentially of an adsorptive material having th empirical formula based on the oxides and which is prepared by reacting a hydrous ox ide or aluminum, a hydrous oxide of silicon, calcium hydroxide and an aqueous solution in 5% concentration of calcium chloride for a period of from 48 to 216 hours at a temperature between 100 and 500' 0., cooling to room temperature and dehydrating.

6. A new composition of matter adapted to adsorb straight chain hydrocarbons consisting essentially of an adsorptive material having the empirical formula based on the oxides and which is prepared by reacting a hydrousoxide or aluminum, a hydrous oxide of silicon. calcium hydroxide and an aqueous solution in 5% concentration or calcium acetate for a period of from 48 to 216 hours at a temperature be 220' and 400 C.. cooling to room temperature and dehydrating.

7. A new composition of matter adapted to adsorb straight chain hydrocarbons consisting essentially of an adsorptive material havin the empirical formula based on the oxides and which is prepared by reacting a hydrous oxide or aluminum, a hydrous oxide of silicon, calcium hydroxide and an aqueous solution in 5% concentration of calcium chloride for a period of from 48 to 216 hours at a temperature between 220 and 400 cooling to room temperature and dehydrating.

8. The method of preparing an adsorbent material having the empirical formula based on the oxides 4CaO.A12Os.4SiOz which comprises reacting together a calcium oxide, a hydrous oxide of aluminum and a hydrous oxide of silicon in the proportion of 4:1:4 for a period from 48 to 216 hours at a temperature between and 500 C.

9. Process according to claim 8 in which the temperature-1s between 220 and 400 C.

10. Process in which the absorbent prepared according to claim 8 is additionally heated under vacuum at a temperature of 500 C.

11. The method of preparing an adsorptive material having the empirical formula based on the oxides 4CaO.Alz0:.4S10a which comprises reacting together calcium hydroxide, a hydrous oxide of aluminum. a hydrous oxide of silicon in the proportion of 4:1:4 and an aqueous solution in about 1 to 10% concentration of a calcium salt for a period of from 48 to 216 hours at a temperature between 100 to 500 C., cooling at room temperature and dehydrating.

12. Process according to claim 11 in which the calcium salt is calcium acetate in 5% concentration.

13. Process according to claim 12 in which the temperature is 220' to 400' C.

14. Process according to claim 11 in which the calcium salt is calcium chloride in 5% concentra- 15. Process according to claim 14 in which the temperature is between 220' and 400 C.

JAMES 1". BLACK.

REFERENCES crran The following references are of record in the file 01' this patent:

, um s'rs rns PATENTS O'IHER- REFERENCES Mellor, Comprehensive Treatise on Inorganic and Theoretical Chemistry, Iongmans. Green a 00., N. Y, 1925, vol. 6. Pages 691 and 692. 

